What about using the Quicktime Ogg Component so you can play them in iTunes and seeing if iTunes can then convert them into mp3s? I don't know if this will work, it's just a suggestion to try.
Convert oggs to mp3s, converting ogginfo tags to id3 tags. Requires: ogg123, ogginfo, id3tool and an mp3 encoder, and nothing else. I've had a bug report that this might be limited to 48 minutes, I'd love more info on this.
Ddoonie, you are the egg man. Many thanks for your astute rec; it worked a treat. One album warned me it was getting "permission errors" when sending its tracks to iTunes...but they arrived there fine, played fine, and burned to CD with no problems.